Last year, the Department of Homeland Security launched a pilot project in Washington DC, deploying a network of sensors to ascertain the extent of cell phone surveillance being conducted in the capitol. They found that not only were International Mobile Subscriber Identity (IMSI) catchers in use, but some were being used in proximity to “potentially sensitive facilities like the White House.”

The revelation comes from a letter sent to Senator Ron Wyden of Oregon, a member of the Select Committee on Intelligence from Christopher C. Krebs, the Senior Official Performing the Duties of the Undersecretary for National Protection and Programs Directorate (NPPD), who was recently nominated to become the directorate’s Undersecretary. In his...